1. Technical Field
This invention generally relates to control mechanisms for gravity flow irrigation systems and more particularly, this invention relates to a one-shot irrigation valve which is normally open in the presence of irrigation water, but which will close in response to an absence of water and remain closed even after a renewed presence of water.
2. Background Art
Recently, the State of Idaho Department of Agriculture implemented regulations which require fertigators and chemigators to employ a "positive shut off valve" in any chemigation employing surface irrigation, an open ditch and a fertilizer gravity flow tank. At the time of the implementation of the regulation and up until the date of the present invention, there was no such device. The State of Idaho delayed the enforcement of the regulation and encouraged development of a device which would satisfy the following criteria:
1. After installation, the positive shutoff valve would be open when the ditch is full.
2. If there is a loss of flow in the ditch, the shutoff valve would close interrupting the flow from the fertilizer tank.
3. If the ditch flow stops and then resumes, the positive shutoff valve stays closed. If siphon tubes are used, the siphon tubes would need to be reset before the nutrient flow could continue. The shutoff valve would stay closed until the siphon tubes are reset preventing fertilizer from passing down the ditch to an off target area potentially resulting in an environmental hazard. After the irrigation system is ready to receive fertilizer, the shutoff valve can be reset.
4. This valve must be corrosion resistant and function with fertilizers which are corrosive products.